[llvm] [RISCV][NFC] Avoid iteration and division while selecting SHXADD instructions (PR #158851)

[Min-Yih Hsu via llvm-commits]

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@@ -25,6 +25,22 @@
 
 namespace llvm {
 
+template <typename T> int isShifted359(T Value, int &Shift) {
+  if (Value == 0)
+    return 0;
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mshockwave wrote:

nit: is this needed?

https://github.com/llvm/llvm-project/pull/158851